Optical refractive index (RI) sensors have been extensively investigated for a number of applications and play a prominent role in biochemical analysis. Among the existing biochemical RI sensors, those based on integrated optical waveguides are of interest because of their high sensitivity, small size, and high scale integration. Recently, RI sensors based on certain types of slot waveguides have attracted interest due to their ability to provide high optical intensity in a subwavelength-scale low refractive index region (slot region). With such slot waveguides, larger light-analyte interaction in the slot region, and hence higher sensitivity, can be obtained as compared to conventional strip waveguides. Up to now, slot waveguide sensors based on ring resonator, Mach-Zehnder interferometer, Bragg grating, and directional coupler have been reported. The reported slot waveguide ring resonator sensors may exhibit sensitivity of about two times larger (about 212 nm/RIU (refractive index unit)) than that of ring resonator sensors based on conventional strip waveguides.
However, it would be beneficial to further enhance the sensitivity of the RI sensor to improve its analyte detectionmeasurement abilities in order to detectmeasure biomolecules with very low detection threshold for example. In addition, because of the complex nature of most biological interactions, it would also be beneficial to provide an RI sensor capable of wavelength multiplexed measurements.
A need therefore exists to provide a reflective index (RI) sensor for analyzing an analyte which is highly sensitive, and preferably also capable of wavelength multiplexed measurements. It is against this background that the present invention has been developed.